JP2003323115A - Image encrypting method, image decrypting method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique capable of protecting contents of image data. <P>SOLUTION: An image encrypting device 2a derives spectral reflectance of an original surface on the basis of acquired original image data 51, built-in light source data 52 and basis function data 53 and obtains weighted coefficients σ<SB>1</SB>, σ<SB>2</SB>, σ<SB>3</SB>of each pixel as object color component data 54. A file including the basis function data 53 used in calculating the spectral reflectance is stored as a key file 61, and a file including the object color component data 54 is stored as an encryption file 62. If the key file and the encryption file 62 are separately used, the former original image data 51 can not be reproduced. Meanwhile, the key file 61 and the encryption file 62 are used in a correct combination, the original image data 51 can be reproduced. Thus, it is possible to protect the contents of the original image data. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a technique for encrypting image data.

[0002]

2. Description of the Related Art In recent years, with the development of data communication technology using a network, information transmission using image data has been frequently performed. On the other hand, it is important to ensure information security in data communication using a network.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
There is a demand for a technique for protecting the contents of image data so that the contents are not leaked to an unspecified number of people.

The present invention has been made in view of the above problems, and an object thereof is to provide a technique capable of protecting the contents of image data.

[0005]

In order to solve the above-mentioned problems, the invention of claim 1 is an image encryption method for encrypting image data of an object to be imaged, wherein a plurality of spectral reflectances of the object to be imaged are provided. One of the basis function and the plurality of weighting coefficients, the coefficient deriving step of deriving the plurality of weighting coefficients from the image data of the imaging target using a predetermined basis function to be expressed as a weighting coefficient of A first file generating step of generating a first file including the key data, where a part is key data, and a second file including data excluding the key data of the basis function and the plurality of weighting factors And a second file generation step for generating.

According to a second aspect of the present invention, in the image encryption method according to the first aspect, the key data is a key coefficient which is one of the plurality of weight coefficients, The file No. 2 is characterized in that alternative data of the key coefficient different from the value of the key coefficient is included.

The invention according to claim 3 further comprises the step of accepting watermark information intended for a digital watermark in the image encryption method according to claim 2, wherein the substitute data is the key coefficient. It is generated based on the watermark information.

According to a fourth aspect of the present invention, there is provided an image decoding method for decoding encrypted image data of an image pickup target, which comprises a predetermined basis function and a plurality of predetermined basis functions for expressing the spectral reflectance of the image pickup target. Based on a first file containing a part of the key data of the weighting factors of and a second file containing the basis function and data excluding the key data of the plurality of weighting factors, An image reproduction step of reproducing image data related to an imaging target.

According to a fifth aspect of the present invention, there is provided a program for encrypting image data of an image pickup target, wherein the computer executes the program so that the computer is weighted by a plurality of spectral reflectances of the image pickup target. A coefficient deriving step of deriving the plurality of weighting coefficients from the image data of the imaging target using a predetermined basis function for expressing as a coefficient, and a part of the basis function and the plurality of weighting coefficients. A first file generating step of generating a first file including the key data as key data, and a second file including data of the basis function and the plurality of weighting factors excluding the key data Second
And a file generation step.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

<1. First Embodiment><1-1. System Configuration> FIG. 1 is a diagram showing a schematic configuration of a network system 1 applied to an embodiment of the present invention. As shown in the figure, the network system 1
Is configured by connecting a plurality of MFPs (Multi Function Peripheral) 2 which are multifunctional machines having functions of a scanner, a copying machine, a printer, etc. to a network 3 such as the Internet.

Each of the MFPs 2 has a data communication function via the network 3, and image data etc. can be transmitted and received between the MFPs 2. Further, the MFP 2 has a function of encrypting image data used for data communication or decrypting the encrypted image data.

When the image data is transmitted via the network 3, the MFP 2 on the transmitting side encrypts the image data and transmits the resulting encrypted file,
The original image data is reproduced by decrypting the encrypted file received by the MFP 2 on the receiving side. In the following description,
The MFP 2a functions as an image encryption device, and the MFP 2b
Let us consider a situation in which the device functions as an image decoding device. However,
These relationships are not fixed, and the MFP 2b may function as an image encryption device and the MFP 2a may function as an image decryption device in some cases.

Although only two MFPs 2 are shown in FIG. 1, a large number of MFPs 2 may be connected to the network 3 or other data communication devices may be connected. Multiple MFPs 2 on network 3
, The MFP 2 can function as an image encryption device or an image decryption device.

<1-2. Configuration of MFP> FIG.
2 is a perspective view showing 2 (image encryption device 2a, image decryption device 2b). FIG. As shown in the figure, the MFP 2 mainly displays an operation panel 21 that displays various information and receives an operation from a user, a scanner unit 23 that photoelectrically reads an original document to be imaged to obtain image data, and a recording unit. Printer unit 2 for printing image data on a sheet
It is equipped with 4.

Further, a paper feed tray 28 for supplying recording sheets to the printer section 24 is arranged in the lower part of the main body of the MFP 2, and a discharge tray 29 for discharging the recording sheets printed by the printer section 24 is arranged in the center part. On the upper part of the main body, a top cover 27 which has a function as a document feeding device (feeder device) for feeding the document to the scanner section 23 and which can be opened and closed is provided.

Further, inside the MFP 2, a data communication section 25 for transmitting and receiving various data via the network 3, and a memory card 9 as an external recording medium.
A card I / F 26 to which the card can be attached and detached is provided. Card I
The / F 26 writes various data to the memory card 9 or reads data recorded in the memory card 9.

The data communication unit 25 has a network I / F, and the network 3 is connected via the network I / F so that various data can be transmitted / received to / from an external device.
Connected to. This causes the MFP 2 to scan the scanner unit 23.
It is possible to transmit the image data acquired by the above or the like to the external device via the network 3, and it is also possible to receive the image data transmitted from the external device.

The operation panel 21 includes a plurality of operation buttons 21.
a and a color liquid crystal display 21b.
The display 21b has a function as a touch panel, and the user can directly operate the screen. While confirming the content displayed on the display 21b, the user can input the document reading, the setting of the transmission mode of the image data, etc. to the MFP 2 through the operation buttons 21a and the display 21b as a touch panel.

The MFP 2 has, as image data transmission modes, a normal transmission mode for directly transmitting the image data acquired by the scanner unit 23 and an encrypted transmission mode for transmitting an encrypted file obtained by encrypting the image data. Either transmission mode can be selected via the operation panel 21.

The printer unit 24 prints an image on a recording sheet supplied from the paper feed tray 28 based on the image data acquired by the scanner unit 23, the image data received via the data communication unit 25, and the like. Print in color.

The scanner unit 23 photoelectrically reads image information from a document such as a photograph, a character or a picture to generate image data. FIG. 3 is a diagram showing an outline of the internal configuration of the scanner unit 23.

Inside the scanner unit 23, two carriages (first carriage 201, second carriage 202) that move along guide rails (not shown) provided in the horizontal direction are provided. First carriage 201
Includes a built-in light source 211 that illuminates the document 8 placed on the contact glass 206, and a first mirror 212 that horizontally reflects reflected light from the document 8 illuminated by light from the built-in light source 211. ing. On the other hand, the second carriage 202 includes a second mirror 213 that reflects the reflected light beam from the first mirror 212 downward and a third mirror 214 that further reflects the reflected light beam from the second mirror 213 in the horizontal direction. ing.

A lens 203 and a CCD 204 are arranged at appropriate positions below the scanner unit 23. C
The CD 204 has three line sensors having different reading wavelengths, and the three line sensors correspond to R, G, and B colors, respectively. Therefore, the CCD 204 can acquire the values for each color of R, G, B as the value of each pixel.

At the time of reading the original 8, the first carriage 201 is driven by a stepping motor (not shown), and the original surface is scanned while repeating horizontal movement / stop for each line. On the other hand, the second carriage 202
Is driven so that the optical path length until the reflected light from the document surface is received by the CCD 204 is constant. In the stopped state during this scanning, the reflected light for one line is received by each of the three line sensors of the CCD 204, and the values of R, G, and B colors are acquired.

When the top cover 27 is in the closed state,
The scanner unit 23 is arranged so as to cover the upper surface of the contact glass 206. This prevents light (steady light) from the outside of the apparatus from entering the scanner unit 23 when reading the document 8. Whether the top cover 27 is closed or open is detected by the top cover sensors 207 provided on the top cover 27 and the top surface of the scanner unit 23, respectively. Top cover sensor 207
Detects the state of the top cover 27 by detecting contact / non-contact between the sensors.

FIG. 4 is a block diagram schematically showing a configuration of the MFP 2 for mainly performing the process according to the present embodiment.

In the structure shown in FIG. 4, the lenses 203, C
CD 204, A / D converter 205, operation panel 21, C
The PU 31, the ROM 32, and the RAM 33 realize the function of acquiring image data. That is, when an original reading instruction is given from the operation panel 21, the reflected light from the original is imaged on the CCD 204 by the lens 203, and the CCD 2
The image signal from 04 is digitally converted by the A / D conversion unit 205. The digital image signal converted by the A / D converter 205 is stored in the RAM 33 as image data. These operation controls are performed by the CPU 31 operating according to the program 321 stored in the ROM 32. The image data acquired in this way is stored in the fixed disk 35, or
It is stored in the memory card 9 by the card I / F 26.
Then, the data is printed by the printer unit 24 or transmitted to the external MFP 2 or the like connected to the network 3 by the data communication unit 25 as necessary.

The CPU 31 is also connected to a drive system (not shown in FIG. 4) such as a built-in light source 211 in the scanner unit 23 and a stepping motor, which are also connected to the CPU 31.
Controlled by. In addition, the upper surface cover sensor 207
(Not shown in FIG. 4) is also connected to the CPU 31, and a signal indicating the energization of the upper surface cover sensor 207 is input to the CPU 31.

The CPU 31, ROM 32 and RA
M33 realizes various functions by software. Specifically, the program 32 stored in the ROM 32
1, various functions are realized by the CPU 31 performing arithmetic processing while using the RAM 33 as a work area. The program 321 can be stored in the ROM 32 by being read from the memory card 9 or downloaded from a predetermined server storage device connected to the network 3 via the data communication unit 25. The MFP 2 functions as an image encryption device or an image decryption device by the arithmetic processing of the CPU 31 according to the program 321.

<1-3. Image Encryption Device> FIG. 5 shows the CPU 31, ROM 32 and RAM of the image encryption device 2a.
FIG. 33 is a block diagram showing the configuration of functions realized by 33 together with other configurations. In the configuration shown in FIG. 5, the image encryption unit 310 and the serial number generation unit 320 are the CPU
This is a function realized by 31 or the like. The object color component derivation unit 311, the key file generation unit 312, and the encryption file generation unit 313 illustrated in FIG.
The respective functions of are shown. Details of these functions will be described below.

FIG. 6 is a diagram showing a flow of image encryption processing for encrypting image data of the image encryption apparatus 2a set in the encryption transmission mode. The operation of the image encryption device 2a will be described below with reference to FIGS.

First, a document is scanned while the built-in light source 211 emits light from the built-in light source, and image data of the document (hereinafter,
It is called "original image data". ) To get. That is,
The built-in light source light illuminates the document surface for each line, and the reflected light from the illuminated document surface is reflected by the plurality of mirrors 212 to 214.
Then, the light is received by the CCD 204 via the lens 203. The image signal from the CCD 204 is the A / D conversion unit 205.
After being converted into digital data by, the data is transmitted to the RAM 33. By performing such a reading operation on the entire document surface, the document image data 51 is finally RA
It is stored in M33 (step S1). The built-in light source light emitted from the built-in light source 211 at the time of acquiring the original image is controlled so that its spectral distribution is kept constant.

If the upper cover 27 is opened when the original image data 51 is acquired, the ambient light outside the apparatus enters the scanner unit 23 and the original image data 5
1 is affected by the stationary light. When the original image data 51 is affected by the stationary light, it is impossible to perform highly accurate calculation in the subsequent calculations. For this reason, when the top cover 27 is open before reading the original, a screen instructing to close the top cover 27 is displayed on the display 21b, and the top cover 2 is displayed by the user.
After 7 is closed, the document image data 51 is acquired.
Therefore, the document image data 51 is acquired as image data in which only the built-in light source light is used as the illumination light.

When the manuscript image data 51 is stored in the RAM 33, the object color component deriving unit 311 of the image encryption unit 310 then converts the pixel values represented by the RGB values of the manuscript image data 51 into the CCD 204. It is converted into a tristimulus value (XYZ value) in the XYZ color system by a predetermined matrix calculation considering the characteristics. Further, the spectral reflectance of the document is obtained from the document image data 51 converted into XYZ values by using the basis function data 53 including a predetermined basis function. The principle of obtaining the spectral reflectance of the original will be described below.

First, when the wavelength in the visible region is λ and the spectral distribution of the illumination light for illuminating the document is E (λ), this spectral distribution E (λ) is three basis functions E ₁ (λ), E ₂ (λ), E
_{Using 3} (λ) and weighting factors ε ₁ , ε ₂ , ε ₃ ,

[0037]

[Equation 1]

It is expressed as Similarly, a pixel (hereinafter,
It is called "target pixel". ), Where S (λ) is the spectral reflectance at the position on the document, the spectral reflectance S (λ) has three basis functions S ₁ (λ), S ₂ (λ), S ₃ (λ) and Using the weighting factors σ ₁ , σ ₂ , and σ ₃ ,

[0039]

[Equation 2]

It is expressed as Therefore, the CCD 204
The light I (λ) incident on the target pixel of

[0041]

[Equation 3]

It is expressed as Here, X of the target pixel,
Let the three stimulus values of Y and Z be ρ _X , ρ _Y , and ρ _Z , respectively,
The color matching functions of the XYZ color system are R _X (λ), R _Y (λ), R _Z (λ)
Then, ρ _X , ρ _Y and ρ _Z are

[0043]

[Equation 4]

It is expressed as follows. That is, X of the target pixel,
Letting ρ _c be a stimulus value (hereinafter, referred to as “target stimulus value”) relating to either Y or Z, and R _c (λ) being a color matching function corresponding to the target stimulus value, the value ρ _c is

[0045]

[Equation 5]

It can be expressed as

In equation 5, the basis functions E _i (λ) and S _j (λ)
And the color matching function R _c (λ) is a predetermined function.
Further, since the original is illuminated by the built-in light source light with a uniform intensity regardless of the position on the original, the three weighting factors ε _i of the spectral distribution E (λ) of the illumination light are values obtained in advance by measurement. Is. This information is stored in advance in the ROM 32 or RA.
It is stored in M33. Of these, the spectral distribution E of the illumination light
The basis function E _i (λ) expressing (λ) and the weighting coefficient ε _i are stored as the built-in light source data 52 indicating the spectral distribution of the built-in light source light. The basis function S _j (λ) for expressing the spectral reflectance S (λ) of the document is stored as basis function data 53.

Therefore, in the equation shown in Equation 5,
There are three weighting factors σ₁, Σ₂, Σ ₃Only. Well
In addition, the equation shown in Equation 5 is ρ at the target pixel_X, Ρ_Y, Ρ
_ZCan be calculated for each of the three stimulus values of
By solving these three equations,
Number σ₁, Σ₂, Σ₃Is required.

Three determined weighting factors σ ₁ , σ ₂ and σ ₃
And the basis function S _j (λ) are substituted into Equation 2, the spectral reflectance S (λ) at the position on the original corresponding to the target pixel can be expressed. Therefore, the weighting coefficient σ ₁ of the target pixel,
Obtaining σ ₂ and σ ₃ is substantially equivalent to obtaining the spectral reflectance S (λ) at the position on the original corresponding to the target pixel.

Based on the above-described principle of obtaining the spectral reflectance of the original, the object color component deriving unit 311 obtains the weighting coefficients σ ₁ , σ ₂ , and σ ₃ at each pixel of the original image data 51. The calculated weighting factors σ ₁ , σ ₂ , and σ of each pixel
₃ is stored in the RAM 33 as the object color component data 54 (step S2).

When the object color component data 54 is obtained, next, the image encryption unit 310 causes the serial number generation unit 3 to operate.
The serial number is acquired from 20 (step S3).
The serial number is generated every time the document is scanned by the serial number generation unit 320 monitoring the operation of the scanner unit 23, and thus is a unique number for each document scan. That is, the serial number is a unique number to the original image data 51.

Subsequently, the key file 53 is generated by the key file generation unit 312 of the image encryption unit 310.
Specifically, a file including the serial number 71 acquired from the serial number generation unit 320 and the basis function data 53 used when deriving the object color component data 54 is generated as the key file 61. . The generated key file 61 is stored in the fixed disk 35 (step S4).

Subsequently, the cipher file generation unit 313 of the image encryption unit 310 generates a cipher file. Specifically, a file including the serial number 72 acquired by the serial number generation unit 320 and the obtained object color component data 54 is generated as the encrypted file 62. The generated cipher file 62 is stored in the fixed disk 35 similarly to the key file 61 (step S5).

By the way, from the above document image data 51
Weighting coefficient σ₁, Σ₂, Σ₃Contrary to the method of finding
Number σ₁, Σ₂, Σ₃To reproduce the original document image data 51 from
Assuming that, first, the spectral reflectance S of each pixel is
It is necessary to derive (λ). Then, the spectral reflection of each pixel
To derive the emissivity S (λ), the weighting coefficient σ₁, Σ₂, Σ
₃Basis function S used to find_j(λ) is required. You
That is, in order to reproduce the original document image data 51,
Basis function S_j(λ) and three weighting factors σ of each pixel₁, Σ
₂, Σ₃Is required, and even if any of the data is missing, the original
It is impossible to reproduce the image data 51.

Therefore, one of the basis functions S _j (λ) and the three weighting factors σ ₁ , σ ₂ , and σ ₃ is used as key data, and a file containing this key data is generated. , If the files including the data excluding the key data are generated and managed separately, the original document image data 51 cannot be reproduced, and the document image data 51 can be substantially encrypted. .

Therefore, as described above, in the image encryption apparatus 2a of the present embodiment, the basis function S _j (λ) is used as key data, and this key data is used as the key file 61.
On the other hand, the three weighting factors σ ₁ , σ ₂ and σ ₃ are stored as the cipher file 62. As a result, the document image data 51 can be encrypted by a relatively simple calculation to protect the content of the document image data 51.

When decrypting the encrypted file 62 (described later), only the key file 61 generated at the same time can be used, so that the original image data 51 is not used.
The same serial numbers 71 and 72, which are unique numbers to the above, are embedded in the encryption file 62 and the key file 61, respectively. By referring to the embedded serial number, it is possible to identify that the encryption file 62 and the key file 61 are generated at the same time. As a result, the serial number becomes identification information, and the correspondence between the encryption file 62 and the key file 61 can be clarified.

The encrypted file 62 generated as described above is transmitted by the data communication section 25 to the image decoding apparatus 2b designated by the user via the network 3. On the other hand, the key file 61 is stored in the memory card 9 by the card I / F 26 and separately sent to the administrator of the image decoding device 2b by mail or the like. Cryptographic file 6
2 and the key file 61 cannot reproduce the original document image data 51 by themselves. Therefore, by sending the image data to the image decryption apparatus 2b by different methods as described above, the original image data 51 can be obtained even if there is some illegality during the transmission of the encrypted file 62.
It is possible to protect the contents of and prevent the leakage of information.

<1-4. Image Decoding Device> Next, the operation of the image decoding device 2b for reproducing the original document image data using the encryption file 62 and the key file 61 generated in the image encryption device 2a as described above will be described.

FIG. 7 shows the CPU 31 of the image decoding device 2b,
It is a block diagram which shows the structure of the function implement | achieved by ROM32 and RAM33 with another structure. In the configuration shown in FIG. 7, the image decoding unit 330 is a function realized by the CPU 31 and the like. Further, the file designation receiving unit 331, the key file determining unit 332, and the reproduced image generating unit 333 illustrated in FIG. 7 respectively indicate the functions of the image decoding unit 330. Details of these functions will be described below.

As shown in FIG. 7, to the fixed disk 35 of the image decryption apparatus 2b, the encrypted file 62 received by the data communication unit 25 from the image encryption apparatus 2a via the network 3 and the mail are sent by mail or the like. The key file 61 read by the card I / F 26 from the memory card 9 is stored. Although only one encryption file 62 and one key file 61 are shown in the figure for simplification, the encryption file 62 and the key file 6 are shown.
It is assumed that a plurality of 1 are stored in the fixed disk 35.

FIG. 8 is a diagram showing the flow of the image decoding process for reproducing the original document image data using the encryption file 62 and the key file 61 of the image decoding device 2b. Hereinafter, the operation of the image decoding device 2b will be described with reference to FIGS. 7 and 8.

First, the user specifies the encrypted file 62 to be decrypted via the operation panel 21. The designation instruction is accepted by the file designation accepting unit 331, and the designated encryption file 62 is read out to the RAM 33 (step S11).

Next, under the control of the file designation receiving unit 331, a screen for designating the key file 61 used for decryption is displayed on the display 21b of the operation panel 21 (step S12). The user refers to this screen,
Key file 61 corresponding to the specified encryption file 62
Is specified. At this time, if the key file 61 is not designated, the original document image data cannot be reproduced in the subsequent processing, so an error message is displayed on the display 21b (step S15), and the processing ends.

On the other hand, when the key file 61 is designated, the designation instruction is accepted by the file designation accepting unit 331, and the designated key file 61 is stored in the RAM.
33. Then, the key file determination unit 332 determines whether or not the serial number 72 included in the designated encrypted file 62 and the serial number 71 included in the designated key file 61 match (step S13). .

As described above, in the image encryption device 2a, the same serial number is embedded as the identification information in the encryption file 62 and the key file 61 which are simultaneously generated. That is, if it is a combination of the encryption file 62 and the key file 61 that are simultaneously generated,
The serial number 72 and the serial number 71 should match.

However, when the serial numbers 72 and 71 do not match, the encrypted file 62 generated at the same time
Since there is a high possibility that the key file 61, instead of the combination of the key file 61 and the key file 61, has been illegally obtained, in such a case, an error message is displayed on the display 21b (step S15) and the process is terminated. .

As described above, when the serial numbers, which are the identification information, do not match, it is possible to check the validity of the key file 61 by not performing the subsequent reproduction process of the document image data, and it is illegal. Key file 61
Can be prevented.

On the other hand, when the serial numbers 72 and 71 match, the reproduction image generation unit 333 reproduces the document image data. Specifically, the basis function data 53 (the basis function S _j (λ)) in the key file 61 is acquired, and the object color component data 54 (the weighting coefficients σ ₁ and σ _{2 of} each pixel) in the encryption file 62 are acquired. , Σ ₃ ) is acquired. Then, the calculation of Formula 2 is performed for each pixel to obtain the spectral reflectance S (λ) at the position on the document corresponding to each pixel, and further the formulas 3 and 4 are calculated to obtain the final value. Specifically, the tristimulus values ρ _X , ρ _Y , ρ _Z (XYZ values) of each pixel are obtained. As a result, reproduction image data 82 for reproducing the original document image data is generated (step S1).
4).

XYZ color coordinates used in the operations of Equations 3 and 4
Color matching function R of the system_X(λ), R_Y(λ), R _Z(λ) and
Basis function E expressing the spectral distribution E (λ) of bright light_i(λ) and
And weighting coefficient ε_iIs stored in the ROM 32 or the RAM 33 in advance.
To be done. Of these, the basis function E_i(λ) and weighting factor ε_i
Is stored in the RAM 33 or the like as the illumination component data 81.
It As the illumination component data 81, the image decoding device 2
b) Built-in light source spectral distribution, "CIE D65 light source"
Spectral distribution of standard light source such as "CIE D50 light source"
The data shown may be used. However, the original original image is strictly
In order to reproduce the image data, the illumination component data 81
The spectral distribution of the light from the built-in light source of the image encryption device 2a is used.
It is preferable. Therefore, the built-in image encryption device 2a
The light source data 52 is used as the illumination component in the image decoding device 2b.
Separate image decoding device so that it can be used as data 81.
The key file 61 may be sent to the storage device 2b.
Alternatively, it may be included in the encryption file 62.
Yes. The user also specifies the illumination component data 81 to be used.
You may be able to do so.

The reproduced image data 82 thus generated is stored in the RAM 33 and then displayed on the display 21b.
And is printed on the recording sheet by the printer unit 24 as needed. This allows the user of the image decoding device 2b to browse the content of the original document image data.

If the serial number 71 of the key file 61 is illegally rewritten, it may not be possible to prevent the unauthorized use of the key file 61 by checking the validity of the key file 61 in step S13. However, even in such a case, the basis function S _j (λ) in the key file 61 is
It is impossible to generate the normal reproduction image data 82 if it is not the one that was used at the time of generation of 2. Therefore, the serial number 71 of such a key file 61
Even if the document is rewritten illegally, the content of the original document image data can be protected.

<2. Second Embodiment> Next, a second embodiment of the present invention will be described. In the first embodiment, the basis function S _j (λ) necessary to reproduce the original document image data and the three weighting factors σ ₁ , σ ₂ , and σ ₃ of each pixel are the basis. Although the function S _j (λ) is used as the key data, in the present embodiment, the weighting coefficient σ
One of the weighting factors σ ₁ of ₁ , σ ₂ and σ ₃ is used as key data.

The network system 1 applied to the present embodiment is the same as that shown in FIG. 1, and the MFP 2 serving as the image encryption device 2a or the image decryption device 2b.
The configuration of is also similar to that shown in FIGS. Therefore, in the following description, the points different from the first embodiment will be mainly described.

<2-1. Image Encryption Device> FIG. 9 shows the CPU 31 and the ROM 3 of the image encryption device 2a according to the present embodiment.
2 is a block diagram showing the configuration of functions implemented by the RAM 2 and the RAM 33 together with other configurations. Of the configuration shown in FIG. 9, the image encryption unit 310 and the serial number generation unit 320
The encrypted area reception unit 340 is a function realized by the CPU 31 and the like. Further, in FIG. 9, the alternative data generation unit 3 shown together with the object color component derivation unit 311, the key file generation unit 312, and the encryption file generation unit 313.
Reference numeral 14 indicates the function of the image encryption unit 310.

FIG. 10 is a diagram showing the flow of image encryption processing of the image encryption apparatus 2a of the present embodiment. The operation of the image encryption device 2a according to the present embodiment will be described below with reference to FIGS. 9 and 10.

First, similarly to the first embodiment, after the original image data 51 is acquired and stored in the RAM 33 (step S21), the object color component deriving unit 311 causes the basis function data 53 (the basis function) to be obtained. Object color component data 54 (weighting coefficient σ in each pixel) based on S _j (λ)
₁ , σ ₂ , σ ₃ ) is obtained (step S22). Then, the image encryption unit 310 causes the serial number generation unit 3
The serial number serving as identification information is acquired from 20 (step S23).

Next, of the obtained weighting factors σ ₁ , σ ₂ , and σ ₃ in each pixel, one weighting factor σ ₁ is used as key data (hereinafter referred to as “key factor data”), and this key is used. A file including the coefficient data 55 and the acquired serial number 71 is generated by the key file generation unit 312 as the key file 63. The generated key file 63 is stored in the fixed disk 35 (step S
24).

Next, under the control of the encrypted area receiving unit 340, a screen for inquiring whether or not to specify an area to be encrypted in the original image data 51 is displayed on the display 2.
1b is displayed (step S25). In the first embodiment, the entire area of the original image data 51 is the area to be encrypted. However, in the present embodiment, the area to be encrypted (hereinafter, “encrypted area”). The user can specify ".".

When the selection of designating the encrypted area is made, a screen for designating the encrypted area in the original image data 51 is displayed on the display 21b by the control of the encrypted area receiving unit 340. FIG. 11 is a diagram showing an example of a screen for designating such an encrypted area. The user
By referring to the original image data 51 displayed on the display 21b, two diagonal points of a desired area 73 to be an encrypted area are designated by the operation buttons 21a or the like. As a result, the designated area 73 is accepted by the encrypted area accepting unit 340 and is determined as the encrypted area. Figure 1
In the example shown in FIG. 1, the area 73 including the vase in the original image data 51 is designated as the encrypted area (step S26).

On the other hand, when the selection is made without designating the encrypted area, the screen shown in FIG. 11 is not displayed and the entire area of the original image data 51 is determined as the encrypted area (step S27).

When the encrypted area is determined, the alternative data generation unit 314 next determines it as the key coefficient data 55 of the object color component data 54 (weighting coefficients σ ₁ , σ ₂ , σ ₃ in each pixel). weighting factor sigma ₁ value is changed with a new weighting factor sigma _1d as a weighting factor sigma ₁ of substitute data is generated. Specifically, the value of weighting factor sigma ₁ to a predetermined value, or the like to a random value, a weighting factor sigma _1d of difference from the value of the weighting factor sigma ₁ is generated (step S28).

This weighting coefficient σ _1d is included in the object color component data instead of the original weighting coefficient σ ₁ . Therefore, hereinafter, the weighting coefficient σ _{1d is referred} to as “dummy coefficient”, and the object color component data including the dummy coefficient is referred to as “dummy object color component data” 56.

This weighting coefficient σ₁Changing the value of
It is performed only for pixels in the encoded area. Therefore, you
If the encrypted area is specified by the user, the original weighting factor
Number σ ₁And dummy coefficient σ_1dThen, the pixels in the encrypted area
Value is different only for other pixels, and the value is the same for other pixels
Will be done.

Next, the cipher file generator 313
A serial number 72, dummy object color component data 56,
The file including the basis function data 53 is the encrypted file 6
4 is generated. Therefore, the encrypted file 64
Is a basis function S _j (λ) necessary for deriving the spectral reflectance S (λ) of each pixel and three weighting factors σ ₁ , σ ₂ ,
This is a file that includes data excluding the weighting coefficient σ ₁ that is the key coefficient data 55 of σ ₃ and the dummy coefficient σ _1d . The generated cipher file 64 is the key file 63.
Is stored in the fixed disk 35 in the same manner as (step S2)
9).

Then, the generated cipher file 64 and key file 63 are sent to the image decoding apparatus 2b by different methods as in the first embodiment.

Here, it is assumed that the original document image data is reproduced only from the encrypted file 64 generated as described above. The cryptographic file 64 contains the basis function S
_{Since j} (λ) and the three weighting factors σ _1d , σ ₂ , and σ ₃ are included, some image data is generated by performing the same calculation as that of the image decoding device 2b of the first embodiment. It is possible to do so. However, since the dummy coefficient σ _1d is included in one of the weighting coefficients, it is impossible to normally reproduce the original document image data. Therefore, the original image data 51 is substantially encrypted, and the contents of the original image data 51 can be protected.

When the encrypted area is designated, the dummy coefficient σ _1d is different from the original weighting coefficient σ ₁ only for the pixels in the encrypted area, so that substantially only the encrypted area is used. Encrypted. FIG. 12 shows an encrypted file 64 generated from the document image data 51 shown in FIG. 11 (more accurately, image data generated only from the encrypted file 64). As shown in the figure, the encryption file 64
The encrypted area 73 in is in a masked state, and its contents cannot be known. When the encrypted area is designated in this way, it is possible to effectively protect only the contents of the desired area in the document image data 51. For example, when only the area containing important information is desired to be protected, etc. Is effective in.

<2-2. Image Decryption Device> Next, the operation of the image decryption device 2b for reproducing the original document image data using the encryption file 64 and the key file 63 generated in the image encryption device 2a as described above will be described.

FIG. 13 shows the image decoding apparatus 2 of this embodiment.
It is a block diagram which shows the structure of the function implement | achieved by CPU31, ROM32, and RAM33 of b with other structures. Similarly to the first embodiment, the image decoding device 2b
A plurality of encryption files 64 and key files 63 sent from the image encryption apparatus 2a are stored in the fixed disk 35 of FIG.

FIG. 14 is a block diagram of the image decoding apparatus 2 of this embodiment.
It is a figure which shows the flow of the image decoding process of b. Below, FIG.
The operation of the image decoding device 2b according to the present embodiment will be described with reference to FIG.
The operations of 31 to S33 are the same as steps S11 to S13 of FIG.
The operation is similar to.

That is, first, the designation of the encrypted file 64 is accepted (step S31), then the designation of the key file 63 is accepted (step S32), and it is further determined whether or not the serial numbers match. (Step S33). In these processes, when the key file 63 is not specified (No in step S32), or when the serial numbers do not match (step S3).
If No in 3), an error is displayed (step S3).
5), the process ends.

If the serial numbers match, then the reproduced image generating section 333 reproduces the original image data. Specifically, the dummy object color component data 56 in the encryption file 64 (the dummy coefficient σ _1d and the weighting coefficient σ of each pixel)
₂ , σ ₃ ) and basis function data 53 (base function S
_j (λ)) is acquired, and further, the key coefficient data 55 (weighting coefficient σ _{1 of} each pixel) in the key file 63 is acquired. Then, the dummy coefficient σ _1d and the weighting coefficient σ ₁ are exchanged. As a result, the basis function S _j (λ) and the three weighting factors σ ₁ , σ ₂ , and σ ₃ required for reproducing the original document image data are acquired. Then, the reproduction image data 82 for reproducing the original document image data is generated by the same calculation as in the first embodiment (step S).
34). This allows the user of the image decoding device 2b to browse the content of the original document image data.

Even if the encrypted area is designated, the reproduced image data 8 is reproduced by the same method as described above.
2 is generated. FIG. 15 shows reproduction image data 8 generated by the above method from the encryption file 64 shown in FIG.
2 is shown. As shown in the figure, the reproduced image data 82
In, the mask of the encrypted area 73 is eliminated, and all the pixels of the original document image data (see FIG. 11) are reproduced.

<3. Third Embodiment> Next, a third embodiment of the present invention will be described. In the above embodiment, the content of the original image data is protected, but in this embodiment, the watermark information intended for the digital watermark is embedded in the encrypted file to protect the content of this watermark information.

The network system 1 applied to this embodiment is the same as that shown in FIG. 1, and the MFP 2 serving as the image encryption device 2a or the image decryption device 2b.
The configuration of is also similar to that shown in FIGS. Further, since the key file generated in this embodiment is the same as that in the second embodiment, the second file will be described in the following description.
The differences from the above embodiment will be mainly described.

<3-1. Image Encoding Device> FIG. 16 shows the CPU 31 and the ROM of the image encoding device 2a according to the present embodiment.
32 is a block diagram showing a configuration of a function realized by 32 and a RAM 33 together with other configurations. FIG. Of the configuration shown in FIG. 16, the image encryption unit 310 and the serial number generation unit 3
20 and the watermark image reception unit 350 are functions realized by the CPU 31 and the like.

FIG. 17 is a diagram showing a flow of image encryption processing of the image encryption apparatus 2a of the present embodiment. The operation of the image encryption device 2a according to the present embodiment will be described below with reference to FIGS.

First, similar to the above-described embodiment, after the original image data 51 is acquired and stored in the RAM 33 (step S41), the object color component deriving unit 311 causes
Based on the basis function data 53 (the basis function S _j (λ)) and the like, the object color component data 54 (the weighting coefficient σ ₁ , at each pixel,
σ ₂ , σ ₃ ) is obtained (step S42). And
By the image encryption unit 310, the serial number generation unit 320
A serial number serving as identification information is acquired from (step S43).

Next, of the obtained weighting factors σ ₁ , σ ₂ , and σ ₃ for each pixel, the weighting factor σ ₁ is the key coefficient data 5
A file including the key coefficient data 58 and the acquired serial number 71 is generated as the key file 65 by the key file generation unit 312. The generated key file 65 is stored in the fixed disk 35 (step S44).

Next, under the control of the watermark image receiving section 350, a screen for receiving the watermark information intended for the digital watermark is displayed on the display 21b. Then, the watermark image receiving unit 350 generates the watermark image data 57 based on the watermark information input by the user.
For example, a character string that is desired to be embedded as a digital watermark is input by the operation button 21a or the like, watermark image data 57 is generated based on the input character string, and RAM is generated.
Stored in 33. The watermark image data 57 is image data in which each pixel is represented by a binary value (1 bit),
The bit of the pixel in the area corresponding to the watermark information is set (1
Is set) (step S45).

FIG. 18 is a diagram showing an example of the watermark image data 57. In the example of FIG. 18, “Configide
The watermark image data 57 is generated based on the character string “ntial”. In the watermark image data 57 of FIG. 18, the character string “Confidentia
The bit of the pixel in the area corresponding to "l" is in a raised state.

Note that such watermark information is not limited to a character string, and may be any information as long as it can be expressed as binary image data such as a picture or a symbol. Also, a plurality of watermark image data 5 indicating various watermark information
7 may be stored in advance in the fixed disk 35 or the like so that the watermark information can be selected from them.

When the watermark image data 57 is obtained, the weighting coefficient σ ₁ which is the key coefficient data 58 of the object color component data 54 is next calculated by the alternative data generating section 314.
Values are changed, a new weighting factor sigma _{1 w} as the weighting factor sigma ₁ of substitute data is generated. The weighting coefficient σ _1w is generated based on the key coefficient data 58 and the watermark image data 57.

Specifically, paying attention to one pixel in the watermark image data 57, and if the bit of the pixel of interest is set, the pixel in the object color component data 54 corresponding to this pixel The value of the weighting coefficient σ ₁ of is multiplied by a predetermined change rate (for example, a value other than 1 and a value of 0.9 to 1.1). By performing for all pixels such calculation, weighting factor sigma _{1 w} which slightly differs from the value of the weighting factor sigma ₁ is generated. However, the value is actually changed only in the pixel corresponding to the region where the bit is set in the watermark image data 57 (step S46).

This new weighting coefficient σ _1w is equal to the weighting coefficient σ ₁
In the following, the weighting coefficient σ _{1w is referred} to as a “watermark synthesis coefficient”, and the object color component data including the watermark synthesis coefficient is referred to as a “synthesized object”. This is referred to as "color component data" 59.

Next, the cipher file generator 313
A file including the serial number 72, the composite object color component data 59, and the basis function data 53 is an encrypted file 66.
Is generated as. Therefore, the encryption file 66 is
It is a file containing the basis function S _j (λ), the watermark synthesis coefficient σ _1w, and the weighting coefficients σ ₂ and σ ₃ , and the watermark information is substantially embedded. The generated cipher file 66 is similar to the key file 65 in the fixed disk 35.
(Step S47).

Then, the generated cipher file 66 and key file 65 are sent to the image decoding apparatus 2b by different methods, as in the above embodiment.

Here, the image decryption apparatus 2 of the above-described embodiment is obtained from only the encrypted file 66 in which the watermark information is embedded.
It is assumed that the original document image data is reproduced by the same calculation as in b. In the cipher file 66, the basis function S
_{Since j} (λ), the watermark synthesis coefficient σ _1w, and the weighting coefficients σ ₂ and σ ₃ are included, it is possible to generate image data. Further, the watermark synthesis coefficient σ _1w is a slight modification of the original weighting coefficient σ _1. However, this modification amount is a modification amount that cannot be visually identified by the image data. Therefore, the generated image data reproduces almost the original document image data. However, on the other hand, it is impossible to visually identify the embedded watermark information, and the watermark information (watermark image data) is substantially encrypted. Therefore, the content of the watermark information can be protected.

<3-2. Image Decoding Device> Next, the operation of the image decoding device 2b for extracting watermark information from the encrypted file 66 in which the watermark information generated as described above is embedded will be described.

FIG. 19 shows an image decoding apparatus 2 according to this embodiment.
It is a block diagram which shows the structure of the function implement | achieved by CPU31, ROM32, and RAM33 of b with other structures. Similar to the above-described embodiment, the fixed disk 35 of the image decryption device 2b stores a plurality of encryption files 66 and key files 65 sent from the image encryption device 2a.

FIG. 20 shows the image decoding apparatus 2 of this embodiment.
It is a figure which shows the flow of the image decoding process of b. Below, FIG.
The operation of the image decoding device 2b according to the present embodiment will be described with reference to FIG.
The operations of 51 to S53 are the same as steps S11 to S13 of FIG.
The operation is similar to.

That is, first, the designation of the encryption file 64 is accepted (step S51), then the designation of the key file 63 is accepted (step S52), and it is further determined whether or not the serial numbers match. (Step S53). In these processes, when the key file 63 is not specified (No in step S52), or when the serial numbers do not match (step S5).
If No in 3), an error message is displayed (step S5).
6), the process ends.

If the serial numbers match, then
The reproduction image generation unit 333 reproduces the document image data, but prior to this, the process of extracting the watermark information embedded in the encrypted file 66 is performed. Specifically, the composite object color component data 59 in the encryption file 66
(Watermark synthesis coefficient σ _1w and weighting coefficients σ ₂ , σ _{3 of} each pixel) and basis function data 53 (basis function S _j (λ)) are acquired, and further, key coefficient data 58 in the key file 65.
(Weighting coefficient σ _{1 of} each pixel) is acquired, and the difference between the watermark synthesis coefficient σ _1w of each pixel and the weighting coefficient σ ₁ is calculated. Then, only the pixels in which the difference is generated by this calculation are extracted, and binary image data in which the bits of only the extracted pixels are set is generated.

A pixel having a difference between the watermark synthesis coefficient σ _1w and the weighting coefficient σ ₁ is a pixel in which watermark information is embedded. Therefore, generated image data (hereinafter, referred to as “reproduced watermark image”). It corresponds to the original watermark image data.
That is, the watermark information is extracted by such calculation (step S54).

When the watermark information is extracted, the basis function S _j (λ) and the three weighting factors σ ₁ , σ ₂ and σ _{3 of} each pixel are next extracted.
From the above, reproduction image data for reproducing the original document image data is generated by the same calculation as in the above embodiment. However, a predetermined XYZ value (predetermined color) is given to a pixel corresponding to a pixel in which a bit is set in the reproduced watermark image. As a result, the watermark composite reproduction image data 83 in which the watermark information is extracted is generated (step S55).

FIG. 21 is a diagram showing an example of the watermark synthesis reproduction image data 83 generated from the encrypted file 66 based on the original image data 51 of FIG. 11 and the watermark image data 57 of FIG. As shown in the figure, in the watermark synthesis reproduced image data 83, the character string “Co
"nfidental" has emerged.
As a result, the user of the image decoding device 2b can browse the content of the watermark information.

<4. Fourth Embodiment> Next, a fourth embodiment of the present invention will be described. In the above embodiment, the image encryption process or the image decryption process is performed inside the MFP 2, but it is also possible to perform this process by a computer.

FIG. 22 is a diagram showing a schematic configuration of the network system 10 applied to this embodiment. The network system 10 is configured by connecting a plurality of computers 4 to a network 3 such as the Internet. The computer 4 includes a CPU, ROM, RA
It is composed of a general-purpose computer including an M, a fixed disk, a display and a communication interface. Further, these computers 4 can communicate with each other via the network 3.

The computer 4a is connected to the MFP 2c which acquires the document image data. The configuration of this MFP 2c is the same as that described in the above embodiment,
It does not have an image encryption processing function or an image decryption processing function.

In the present embodiment, the original image data acquired by the MFP 2c is transmitted to the computer 4a via the transmission cable 5 or the like, and the computer 4a generates an encrypted file. Then, the generated encrypted file is transmitted to the computer 4b via the network 3, and the encrypted file is decrypted in the computer 4b. That is, the computer 4a functions as an image encryption device, and the computer 4b functions as an image decryption device. These computers 4a and 4b can be used for the processing of any of the first to third embodiments.

For example, the computer 4a shown in FIG.
When 4b is used for the processing of the first embodiment, the CPU or the like inside the computer 4a performs the arithmetic processing according to the program stored in advance in the fixed disk or the like, so that the image encryption shown in FIG. It functions as the unit 310. On the other hand, the CPU inside the computer 4b is
By performing arithmetic processing according to a program stored in advance on a fixed disk or the like, the image decoding unit 3 shown in FIG.
Function as 30.

When performing the image encryption processing, the MFP 2c
Original image data 51 and built-in light source data 5 acquired from
2 and the serial number are transferred to the computer 4a, and the computer 4a uses these data to generate the key file 61 and the encryption file 62. At this time, the basis function data 53 is stored in advance in a fixed disk or the like of the computer 4a. Generated key file 6
1 and the encrypted file 62 are sent to the computer 4b by different methods. On the other hand, when the image decoding process is performed, the computer 4b generates the reproduced image data 82 for reproducing the original document image data from these data.

Further, the computers 4a and 4 shown in FIG.
When b is used for the processing of the second embodiment, the CPU or the like inside the computer 4a functions as the image encryption unit 310 and the encryption area reception unit 340 shown in FIG. The CPU and the like function as the image decoding unit 330 illustrated in FIG. 13. Similarly,
When the computers 4a and 4b shown in FIG. 22 are used for the processing of the third embodiment, the computer 4a
The internal CPU and the like function as the image encryption unit 310 and the watermark image reception unit 350 shown in FIG. 16, while the internal CPU and the like function as the image decryption unit 330 shown in FIG.

As described above, the computer 4 can perform the image encryption process or the image decryption process of the MFP 2 according to the first to third embodiments. In this case, the general-purpose computer 4 performs the image encryption process. It can be used as an encoding device or an image decoding device.

<5. Modifications> Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made.

For example, in the above embodiments, the image encryption apparatus has been described as being the MFP 2 or the computer 4, but it is also possible to use, for example, a digital camera as the image encryption apparatus. As a method for obtaining the spectral reflectance of a subject from image data in a digital camera, for example, the method disclosed in Japanese Patent Application Laid-Open No. 2001-78202 filed by the present applicant can be used.

In addition, in the second embodiment described above,
Although the weight coefficient σ ₁ is used as the key coefficient data, any of the weight coefficients σ ₁ , σ ₂ , and σ ₃ may be used as the key coefficient data. Also, the weighting coefficient σ ₁ ,
_Two weighting coefficients of σ ₂ and σ ₃ may be used as key coefficient data. Of course, in such a case, the dummy object color component data will include two dummy coefficients.

Further, in the above embodiment, various functions are realized by the CPU performing arithmetic processing according to a program, but all or part of these functions may be realized by a dedicated electric circuit. Good. In particular, a high-speed operation can be realized by constructing a place where a repeated operation is performed with a logic circuit.

The specific embodiments described above include inventions having the following configurations.

(1) The image encryption method according to claim 1, wherein the key data is the basis function.

According to this, the contents of the image data can be appropriately protected by a simple method.

(2) The image encryption method according to claim 2, further comprising an area receiving step of receiving a designation of an encryption area in the image data, wherein the substitute data is in a pixel of the encryption area. An image encryption method, wherein only the value differs from the value of the key coefficient.

According to this, it is possible to protect the contents of the desired encrypted area in the image data.

(3) In the image encryption method according to any one of claims 1 to 3 and (1) and (2), the same identification information is embedded in both the first and second files. An image encryption method, further comprising:

According to this, the correspondence between the first and second files can be clarified.

(4) The image decoding method according to claim 4, wherein the key data is the basis function.

According to this, the contents of the protected image data can be browsed by a simple method.

(5) In the image decoding method according to claim 4, the key data is a key coefficient which is one of the plurality of weight coefficients, and the second file has the above-mentioned An image decoding method, characterized in that alternative data of the key coefficient different from the value of the key coefficient is included.

According to this, the content of the protected image data can be browsed by a simple method.

(6) In the image decoding method according to claim 4 or any one of (4) and (5), the first and second files have the same identification information when they are simultaneously generated. And an identification information determining step of determining whether or not the identification information embedded in advance in each of the first file and the second file used in the image reproducing step matches. The image decoding method further comprising: if the identification information does not match, the image reproducing step is not performed.

According to this, when the identification information does not match, the image reproducing step is not performed, so that it is possible to prevent the use of the first and second files which are an illegal combination.

(7) In the image decoding method described in (5) above, the alternative data is generated based on the key coefficient and watermark information intended for a digital watermark, and the image reproduction is performed. The image decoding method, wherein the step includes a step of extracting the watermark information based on the first and second files.

According to this, the contents of the protected watermark information can be browsed.

(8) A program for decrypting encrypted image data of an object to be imaged, wherein execution of the program by a computer causes the computer to execute a predetermined process for expressing the spectral reflectance of the object to be imaged. A first file including a basis function and a part of key data of the plurality of weighting coefficients, and a second file including data of the basis function and the plurality of weighting coefficients excluding the key data
And a file for reproducing the image data of the imaging target based on the file.

According to this, the content of the protected image data can be browsed.

(9) An image encryption apparatus for encrypting image data of an image pickup target, wherein a predetermined basis function for expressing the spectral reflectance of the image pickup target as a plurality of weighting coefficients is used, Coefficient deriving means for deriving the plurality of weighting factors from the image data of the imaging target, and a part of the basis function and the plurality of weighting factors is used as key data, and a first file including the key data is generated. And a second file generating means for generating a second file including data excluding the key data among the basis function and the plurality of weighting factors. Image encryption device.

According to this, the contents of the image data can be protected.

(10) An image decoding device for decoding encrypted image data of an imaging target, wherein a predetermined basis function for expressing the spectral reflectance of the imaging target and a plurality of weighting coefficients Image data relating to the imaging target based on a first file including some key data and a second file including data excluding the key data among the basis functions and the plurality of weighting coefficients An image decoding device comprising: an image reproducing unit that reproduces the image.

According to this, the content of the protected image data can be browsed.

[0151]

As described above, according to the inventions of claims 1 and 5, the contents of the image data can be protected.

According to the second aspect of the present invention, since the second file includes the alternative data and the correct image data cannot be reproduced only by the second file, the contents of the image data are properly protected. can do.

According to the third aspect of the invention, the content of the watermark information can be protected.

Further, according to the invention of claim 4, the contents of the protected image data can be browsed.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a network system applied to an embodiment of the present invention.

FIG. 2 is a perspective view showing an MFP (image encryption device, image decryption device).

FIG. 3 is a diagram showing an outline of an internal configuration of a scanner unit.

FIG. 4 is a block diagram schematically showing a configuration of an MFP.

FIG. 5 is a block diagram showing a functional configuration of the image encryption apparatus according to the first embodiment.

FIG. 6 is a diagram showing a flow of image encryption processing of the image encryption apparatus according to the first embodiment.

FIG. 7 is a block diagram showing functional functions of the image decoding apparatus according to the first embodiment.

FIG. 8 is a diagram showing a flow of image decoding processing of the image decoding apparatus according to the first embodiment.

FIG. 9 is a block diagram showing a functional configuration of an image encryption apparatus according to a second embodiment.

FIG. 10 is a diagram showing the flow of image encryption processing of the image encryption apparatus according to the second embodiment.

FIG. 11 is a diagram showing an example of original image data.

FIG. 12 is a diagram showing an example of an encrypted file in which an encrypted area is designated.

FIG. 13 is a block diagram showing functional functions of an image decoding device according to a second embodiment.

FIG. 14 is a diagram showing the flow of image decoding processing of the image decoding apparatus according to the second embodiment.

FIG. 15 is a diagram showing an example of reproduced image data.

FIG. 16 is a block diagram showing a functional configuration of an image encryption device according to a third embodiment.

FIG. 17 is a diagram showing the flow of image encryption processing of the image encryption apparatus of the third embodiment.

FIG. 18 is a diagram showing an example of watermark image data.

[Fig. 19] Fig. 19 is a block diagram illustrating functional functions of an image decoding device according to a third embodiment.

FIG. 20 is a diagram showing the flow of image decoding processing of the image decoding apparatus according to the third embodiment.

FIG. 21 is a diagram showing an example of watermark composite reproduction image data.

FIG. 22 is a diagram showing a schematic configuration of a network system according to a fourth embodiment.

[Explanation of symbols]

2a MFP, image encryption device 2b MFP, image decoding device 3 network 8 manuscript 9 memory cards 21 Operation panel 23 Scanner 25 Data Communication Department 61 key file 62 Cryptographic file

Continued front page    F term (reference) 5B057 BA02 CB19 CE08 CE20 CG07                       CH08 CH11 CH12                 5C075 AB90 EE03                 5C076 AA14 BA06                 5J104 AA12 PA14

Claims (5)

[Claims] 1. A method of encrypting image data relating to an image pickup target, comprising: using a predetermined basis function for expressing a spectral reflectance of the image pickup target as a plurality of weighting factors. A coefficient deriving step of deriving the plurality of weighting factors from image data, and a first file for generating a first file including the key data, using a part of the basis function and the plurality of weighting factors as key data An image encryption method, comprising: a generation step; and a second file generation step of generating a second file including data excluding the key data among the basis function and the plurality of weighting factors. . 2. The image encryption method according to claim 1, wherein the key data is a key coefficient that is one of the plurality of weight coefficients, and the second file includes the key coefficient. An image encryption method, characterized in that alternative data of the key coefficient different from the value of the key coefficient is included. 3. The image encryption method according to claim 2, wherein watermark information intended for digital watermarking is received.
The image encryption method, wherein the alternative data is generated based on the key coefficient and the watermark information. 4. A method for decrypting encrypted image data of an imaging target, comprising a predetermined basis function for expressing a spectral reflectance of the imaging target and a part of a plurality of weighting coefficients. Reproducing image data relating to the imaging target based on a first file containing key data and a second file containing data of the basis function and the plurality of weighting factors excluding the key data. An image decoding method comprising: an image reproduction step. 5. A program for encrypting image data relating to an image pickup target, wherein the computer executes the program, and a predetermined value for causing the computer to express the spectral reflectance of the image pickup target as a plurality of weighting factors. A coefficient derivation step of deriving the plurality of weighting factors from the image data of the imaging target using the basis function of, and a part of the basis function and the plurality of weighting factors as key data, and the key data And a second file generation step of generating a second file including data excluding the key data of the basis function and the plurality of weighting coefficients. A program characterized by executing ,.